click here for more details on the retail method, but it's basically just this --
> you fill up your retail with flowers, fruit, any junk really priced at 999k bells
> i can buy two at a time, which means 2 million bells at a time, and then i just keep running back & forth and doing this until we reach the amount you're asking for, which in this case is 10
the only thing you really need to do is make sure retail gets refilled after i buy everything, but otherwise, you don't have to do much of anything other than wait.